In a series of closed-door meetings, Obama and Vice President Joe Biden met with some of the commandos who went on Monday's early-morning raid in Pakistan and with members of the broader assault force that supported the mission.

"I came here for a simple reason: to say thank you on behalf of America," Obama told soldiers at Fort Campbell, the home of the 101st Airborne Division, after his private meetings.

"Thanks to the incredible skill and courage of countless individuals, intelligence, military, over many years, the terrorist leader who struck our nation on 9/11 will never threaten America again," he said.

The president said he had visited New York the day before to pay homage to the victims of bin Laden's 2001 terrorist attacks, as well as to the firefighters and police who responded to the catastrophe.

"I promised that our nation will never forget those we lost that dark September day," he told about 2,000 troops in a steamy hangar.

"And today, here at Fort Campbell, I had the privilege of meeting the extraordinary special-ops folks who honored that promise," he said.

"It was a chance for me to say, on behalf of all Americans and people around the world: Job well done. Job well done."

The commandos briefed Obama personally about the raid, White House aides said, and he gave each of the groups the Presidential Unit Citation, the highest honor he can give a military unit.

"In each meeting, the president was able to speak and offer his personal admiration and gratitude for our service members and to personally greet them," said a White House official, who spoke on condition of anonymity about the private meetings as a matter of policy.

The extraordinary sessions were kept private to protect the identities of those involved and to shield them from becoming targets of terrorist reprisals.

Obama, who was making his first visit to Kentucky as president, then met with the 160th Special Operations Aviation Regiment and the 5th Special Forces Group to thank them for their service.

Underneath a huge American flag and with camouflage netting adorning the stage, the president said he had made the hastily arranged trip to personally thank "the most capable" warriors in the history of the world.

He recognized the 125 soldiers from the base who "have made the ultimate sacrifice" in Afghanistan since early last year.

Obama said the American military had "broken the Taliban's momentum" to promote terrorism in Afghanistan.

"We are ultimately going to defeat al-Qaida," the president said, to loud cheers from the soldiers.

But Obama said he didn't want to fool anyone: "This continues to be a tough fight."

The president, who shed his suit jacket to speak in the warm hangar, recounted a letter he had received Monday from a 14-year-old New Jersey girl who lost her father in the 9/11 attacks on the World Trade Center and the Pentagon.

"We're still the America that does the hard things, the great things," Obama said.